SlIpReleasedAsync_t&SlIpLeasedAsync_t疑問

想請問下面這些代碼的意思，例如MAC是指誰的MAC之類?

typedef struct
{
_u32 ip_address;
_u32 lease_time;
_u8 mac[6];
_u16 padding;
}SlIpLeasedAsync_t;

typedef struct
{
_u32 ip_address;
_u8 mac[6];
_u16 reason;
}SlIpReleasedAsync_t;

＿